In recent years, the amount of information processing required for electronic apparatuses has steadily increased, and the signal speed in electronic apparatuses has significantly increased. Accordingly, the number of layers of a printed wiring board and the thickness thereof have also tended to increase. This causes an increase in the length of a via stub in a through-hole, resulting in the degradation of the signal quality in the via stub due to the resonance of the high-frequency (for example, several gigahertz) components. The via stub is a stub portion (open wiring portion) of a via. Conventionally, the via stub of the through-hole is drilled and removed to reduce the degradation of the signal quality.
Japanese Laid-open Patent Publications Nos. 2003-283093 and 8-97564 disclose a multi-layer printed wiring board with a reduced via stub of a through-hole or a multi-layer wiring board whose surface can be formed flat.